International trains from London, Paris, Brussels, and other countries may be an alternative for some.
Leiden is a small city. The conference venues are in the city center and clos to each other. Most transfers from your hotel to a conference venue can be done on foot or you can rent a bicycle!
There are many restaurants in Leiden.
Like in any city, eating out is very popular. If you have a particular restaurant in mind to visit I advise you to make a reservation a couple of weeks before the conference.